browser_full_page_metrics

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden, and it does disclose the exact return set, which implies a non-mutating read. However it omits whether the call touches the page state and what happens when tab_id is omitted (null default), leaving key behavior to inference.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single front-loaded sentence with no filler; the return payload is stated immediately. It is efficient, though arguably compressed to the point of leaving the tab-selection question unaddressed.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema and no annotations, so the description must carry everything. It adequately conveys the returned metrics but does not cover the undocumented tab_id default or scoping, leaving a real gap for a tool that operates on a specific tab.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0% and the single optional parameter tab_id is never mentioned in the description. The agent cannot tell from either source whether omitting tab_id targets the active tab or fails, so the description does not compensate for the schema gap.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Return document/viewport sizes + scroll position + devicePixelRatio'), which clearly separates it from screenshot and DOM siblings. It is clear about what data comes back, though it never distinguishes itself by name from a neighbouring tool like browser_page_info.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no statement of when to call this versus alternatives such as browser_page_info, browser_bounds, or browser_screenshot. Usage is only weakly implied by the returned payload (measuring page dimensions).

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.